List of topics you will read in this article:
What is DOB?
Why were DOBs produced? (Their little benefits)
What are the disadvantages of DOB lights and why should you not use a DOB driver?
Low efficiency, high heat
Flicker or Flicker
Electric pressure
Connection and electrocution
Low power factor
What alternatives do we have for DOB lights?
- What is DOB?
The term DOB in LED lamps and lights means the driver system on the screen (DRIVER ON BOARD) or the so-called “without driver” and in fact it is a mode that
The external driver is removed from the device and the internal driver is fully compressed on the main LED board. Solving the problem of positioning and occupying a lot of space for LED product drivers led to the production of these products.
At the same time, for components such as electrolytic capacitors, which are very sensitive to temperature, these thermal stresses should be minimized by connecting the drivers separately, otherwise the heat generated
It is transferred by the LED to the internal parts of the drive and causes damage to it.
In DOB or driverless products, in order to reduce production costs, small ICs are used as a substitute for capacitors.
But over time, it became clear that DOBs were not a suitable solution because, on the other hand, many important parts in removing noise and parts that increase the life of the circuit have been removed in these products.
In the following, the main reason for the weakness of DOB lights is discussed.
- Why were DOBs produced? (Their little benefits)
Nowadays, it is no secret that DOBs are old and obsolete technologies. However, before mentioning the disadvantages of these drivers, it is necessary to mention its few advantages.
Generally, the driver of DOB lights is designed as a linear power supply. Since there is no high frequency change in this mode, basically there will be no electromagnetic interference (EMI) in the linear mode.
The absence of EMI has allowed linear power supplies to be designed and manufactured using far fewer components. Less current flow between components as well as the smaller size of the components causes little change in LED optical performance.
The current direction of these drivers is adjusted with small ICs without using electrolytic capacitors.
The weakest component used in the driver with the shortest lifespan determines the actual life of the driver.
Eliminating electrolytic capacitors increases the quality and reliability of the driver to some extent.
- What are the disadvantages of DOB lights and why should you not use a DOB driver?
But now it’s time to mention the many disadvantages and weaknesses of DOB lights.
DOB drivers have many limitations. As mentioned, these limitations have caused DOBs to be recognized as an outdated technology. These restrictions include:
- Low efficiency, high heat
Linear power sources have lower optical efficiency, and the overvoltage in these drivers is released in the form of heat and
It creates additional heat in LED lighting equipment, which generally gradually lowers the quality of LED light output. In fact, DOB lights cannot remove the excess amount of incoming electricity and inevitably turn it into heat.
- The disadvantage of DOB lights – Ecowatt
- Flicker or Flicker
Flicker Free Light is one of the important factors of any lighting system, but this factor is not observed in DOB lighting systems due to the presence of large DC waves in the electricity flow.
Many studies have been done regarding flicker and its effect on the user, and in short, as mentioned in the previous articles.
The presence of flicker in lighting products causes eye fatigue, headache and similar problems for the viewer.
- Electric pressure
Aside from the heat applied to DOB light drivers, these products are also under a lot of electrical stress
Because, as mentioned, they don’t have a great ability to absorb and eliminate unwanted voltages created in AC current, and this shortens their lifespan.
- Connection and electrocution
In addition to the above, in DOB lights, the output current is not properly separated from the components and the main current because the driver is located on the main board and inside the light.
Therefore, all metal surfaces used in the product must be insulated to prevent electric shock. The non-isolation of these lights makes it difficult for even a little moisture or dust to enter
An electric circuit is formed and with the formation of a very weak electrical connection, a leakage current is formed from the circuit. This leakage current is directed to the ground if the ground connection is established
But at the same time, it also activates the mechanism of leakage current fuses and life protection and disconnection of the circuit, and due to the multiplicity of this issue, it is practically impossible to use such protection circuits.
The dangerous point is the use of a metal body and not connecting to the ground, and due to the lack of common ground connection in most buildings, the leakage current causes the body to become electrified and may cause electrocution to an unskilled user.
For the reasons mentioned, most of the manufacturers who use such solutions to reduce the price of the product use insulating body material.
Please note that some manufacturers of DOB products use the grounding part in the design of these products, but due to the fact that this connection is not common in Iran and among consumers, there will still be a risk of electrocution.
- The disadvantage of DOB lights – Ecowatt
- Low power factor
Generally, the power factor of lights that use DOB solution is about 0.5 lower than that.
According to the international standards as well as the national standard of Iran, the power factor should be higher than 0.9 for lights above 30 watts, and it limits the use of such solutions for LED lights to a great extent.
At the same time, the low power factor makes the customers who buy their electricity on demand pay a higher price, and at the same time, they may have to use capacitors to correct the power factor, which is expensive.
The power factor means a part of the power that occupies the capacity of the cable but does not turn into light at the end.
The higher the power factor of the lamp, the lower the amount of reactive power (blocked capacity) and the consumed power is converted into light with a higher percentage.
Now, if the power factor of the lamp is higher, it does not mean longer life or more light. Also, it does not mean less lamp consumption; Because in the nominal power of the lamp, the active power (the merchant’s unblocked capital) is directly measured.
Consider two lamps with equal wattage and different power factor; These two lamps produce the same amount of output light in the environment, but the lamp that has a higher power factor can be fed with a thinner wire.
Therefore, this issue is practically more apparent in cases where the number of lamps is large, and generally, large customers pay more attention to it, because in the wiring of large centers, the cost saved in the diameter of the copper wire justifies this price difference.
In practice, the wire with a larger cross section for a low power factor lamp carries energy that goes to the lamp but does not turn into light and returns again (like the money that was placed in the hands of a playful child).
In the end, we note that the power factor does not have a unit and in the top products, it is greater than 0.9. It is also not recommended to buy equipment with a power factor of less than 0.5.
- What alternatives do we have for DOB lights?
It seems that the biggest weakness of DOB or “driverless” lights is the possibility of leakage current and the risk of electric shock and the existence of flicker or flickering light, as well as the low power factor of these drivers.
In order to reduce the cost, this goal can be achieved by using non-isolated drivers that are still connected externally or internally but outside the LED board and inside the body to the lamp or LED light.
These drivers have the same structure as isolated drivers and at the same time do not have many of their problems due to their better design. They also have more reasonable prices than isolated drivers.
These are the most important points related to the weakness of DOB lights and its disadvantages.